CLAS physics database search results Measurement E151M2112 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 234 -0.2105 0.8183 0.0357 0.85 246 0.8376 0.8793 0.0826 0.95 234 -0.4252 2.6708 0.0493 0.95 258 0.2194 2.4248 0.0361 0.65 126 -1.0645 0.8988 0.0755 0.75 126 1.2747 0.8943 0.0882 0.85 90 0.2613 0.792 0.0345 0.85 222 -0.0036 1.0279 0.03 0.85 234 -0.6645 0.8992 0.0526 0.85 246 0.8536 0.9314 0.0631 0.95 258 -0.1952 1.555 0.0326